In other words, they are so advanced that they can visit us without us knowing, unless they wanted us to know. They can wipe us out without us knowing, unless they wanted us to know.
I am so glad all these are still theoretical.
I would see it highly more probable, that if another life form has (and probably, definitely even, has) reached a state of technological development where they can travel to the stars and beyond, they would have already went through a phase in their development as a race, where they realized
'Hey, maybe it's not a good idea to kill ourselves or others, c'mon, let's work together, evolve and go further!'
I could even speculate that this is one of the requirements of making it to a level of technological and spiritual development where we can unlock the secrets of the universe in mutual assurance that we are not afraid of killing ourselves every day, and save that energy for something more constructive, like building space ships..
I think our best hope is that one day, humanity evolves away from biological bodies. We become hardware. We can now travel as an entire society throughout space for millions or billions of years without a problem. At some point, before the heat death of the universe when we're no longer able to get the energy needed to travel (or even exist), we might come across another race that has also progressed and advanced just like us and our paths happen to intersect.
Just as likely they can wipe us out without caring if we know or knowing that we exist, no different then stepping on an ant as you walk to your car.